1. Field of Endeavor
The disclosure relates to a device for fastening a second burner, SEV burner in short, in a sequentially operated gas turbine arrangement, in which a fuel/air mixture is burnt in a first burner so as to form hot gases which can subsequently be supplied, partly expanded, for a second combustion to the SEV burner which is designed essentially as a flow duct, with a flow duct wall, which has an orifice, through which a fuel supply can be introduced into the interior of the SEV burner, and on which are provided in the axial direction of the orifice, in each case opposite one another, two fastening structures, into which in each case a carrying structure for the further fastening of the SEV burner to an external carrier can be introduced.
2. Brief Description of the Related Art
A gas turbine arrangement with sequential combustion may be gathered, for example, from EP 0 620 362 B1, in which an air compressor unit is followed along a unitary rotor shaft, in the throughflow direction of the gas turbine arrangement, by an annular combustion chamber which is arranged circularly about the rotor shaft and which is fed by a multiplicity of premix burners arranged in an annularly distributed manner with an ignitable fuel/air mixture which is ignited, thus giving rise to hot gases which drive a first turbine stage provided downstream of the annular combustion chamber and connected to the rotor shaft. The hot gases emerging, partly expanded, from the first turbine stage subsequently pass into an annular flow duct, in which the partly expanded hot gases are mixed anew with fuel and, with an autoignitable hot-gas/fuel mixture being formed, are ignited within a second annular combustion chamber surrounding the rotor shaft circularly or annularly. The hot gases thereby arising pass, downstream, into a second low-pressure turbine stage, as it is known, in order to perform further expansion work.
It is appropriate, further, to consider in more detail the second or sequential burner which is designed as a flow duct and is designated, further, as an SEV burner, particularly with regard to the fastening of the flow duct within the gas turbine plant and the thermal and mechanical properties of the flow duct.
An SEV burner 1 known per se, designed as a flow duct, may be gathered from the illustration according to FIG. 2 which, in the exemplary embodiment shown, has a rectangular flow duct cross section and is delimited by four flow duct walls, an upper 1o, a lower 1u, and two lateral flow duct walls 1s. On the upper flow duct wall 1o an orifice 2 is introduced, through which a fuel lance 3 serves for the fuel enrichment of the partly expanded hot gases entering the SEV burner. To mount the fuel lance 3, the latter is inserted from above through the orifice 2 of the flow duct 1, the lance tip 3 terminating and being positioned with a defined play with respect to the upper flow duct wall 1o. The play to be provided between the lance tip and the upper flow duct wall should allow as simple a mounting of the lance tip as possible, but cause as low leakages as possible between the components. The SEV burner 1 has, upstream of its flow duct, a fastening flange 4 which is connected to a first expansion stage, not illustrated any further, of the gas turbine plant, that is to say connected to a first turbine stage. The SEV burner is firmly connected axially, at least on one side, to the gas turbine via the fastening flange 4. For the further fastening of the SEV burner, the latter provides in each case, on its top side 1o, fastening structures of collar-like design in the form of reception rails 5 which are in each case arranged in pairs opposite the orifice 2 along the burner axis A and into which in each case a carrying structure 6 can be axially inserted separately. The carrying structures 6 have provided on them in each case two fastening devices 7 of screw-like or pin-like design which in each case fix the carrying structures 6 to an external carrier 8, projecting beyond the SEV burner 1, of the gas turbine arrangement. As may be gathered from the illustration in FIG. 2, the fuel lance 3 likewise projects through the external carrier 8, a supporting ring 3′ with integrated piston ring serving for ensuring sealing off between the radially inner region and the external carrier 8, particularly in the event of thermally induced dimensional variations which occur, above all, during the starting, but also during the operation, of the gas turbine arrangement. Thus, for example, the fuel lance tip is displaced or bent elastically through the burner in the flow direction, so that, on the one hand, a required minimum play between the external carrier and the fuel lance tip must be provided for this purpose and, on the other hand, so as to avoid leakage streams, it is appropriate to seal off this play with a piston ring which is not illustrated in FIG. 2. Moreover, that flange end 4′ of the flow duct 1 which lies opposite the fastening flange 4 is connected directly to the external carrier 8 via fixing noses 9 provided on the upper duct sidewall 1o, so that the SEV burner 1 is detained axially. By contrast, in the circumferential direction, the SEV burner 1 is fixed in relation to the external carrier 8 by the two carrying structures 6 and the fastening device 7 connected to these.
When the gas turbine arrangement is in an operating situation, very high combustion temperatures and high hot gas flow velocities occur due to the combustion processes taking place in the SEV burner region, so that the flow duct walls of the SEV burner are exposed to extreme load thermally and also mechanically, such as, in particular, the upper flow duct wall 1o, in which is introduced an orifice 2 which weakens the flow duct wall structure and due to which the rigidity of the SEV burner 1 is at least locally reduced. Owing to the reduced surface rigidity in this region, relative movements in the form of vibrations occur between the upper duct sidewall 1s and the fuel lance 3 in the region of their mutual contact on account of the process conditions described above, with the result that surface wear sets in at the contact point both on the SEV burner in the region of the orifice 2 and on the burner lance 3 and may lead not only to local material deterioration, such as, for example, corrosion, etc., but also to increased leaks between the fuel lance 3 and SEV burner 1.